The present invention relates to a switching apparatus, an RF coil, and a magnetic resonance imaging apparatus.
Since a plurality of RF coils (such as a body coil and a head coil) might be used in a magnetic resonance imaging apparatus, there is a need to avoid coupling among these RF coils. Therefore, there might be provided a switching apparatus for eliminating the characteristic as a resonant circuit by shifting a resonant frequency of a resonant loop or cutting the loop. Incidentally, the switching apparatus is generally identified by names such as “Dynamic disabling switch”, a detuner, etc.
Since the frequency of a signal of the magnetic resonance imaging apparatus is relatively high, a radiation loss of energy occurs even in the switching apparatus. Therefore, a patent document 1 discloses a technique wherein a switching apparatus (dynamic disabling switch) is configured by a distributed constant circuit and a coaxial cable low in radiation loss of energy is used as a distributed constant element to thereby suppress the radiation loss.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2004-358259
If, however, the switching apparatus is configured by the distributed constant circuit, then the geometrical size of the switching apparatus is affected by required circuit characteristics. On the other hand, the size of the RF coil may preferably be set in accordance with the size of a subject or a region intended for imaging of the subject. The size of the switching apparatus based on the circuit characteristics, and the size of the RF coil based on the imaging object do not necessarily coincide with each other. Since the switching apparatus is disposed in the RF coil, there is a need to allow one size or the like to coincide with the other size or the like. If the size of the RF coil is increased in accordance with the size of the switching apparatus where the switching apparatus is larger than the RF coil, then it exerts an influence on the mountability of the coil onto the subject. If the coaxial cable of the distributed constant circuit is waved in accordance with the size of the RF coil, for example, then a manufacturing process becomes complex.